TEACHING KIT CONTENTS:

  • Step-by-Step Directions for fabrication
  • one halogen bulb without a glass lens
  • a reasonable number of LEDís
  • Super Glue and compound glue
  • soldering iron with solder wire and flux
  • one piece of 0.2mm aluminum sheet similar to aluminum can material
  • a 3-hole paper punch
  • resistors for LED and the supply voltage combinations
  • online access to http://led.linear1.org/led.wiz, for an LED array calculator to compute the resistors required

TEACHING KIT DIRECTIONS:

    

STEP

    

  

IMAGES

  

DIRECTIONS

    

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Required for this procedure
To assemble an LED: (1) one halogen bulb without a glass lens; (2) a reasonable number of LEDís; (3) Super Glue and compound glue; (4) soldering iron with solder wire and flux; (5) one piece of 0.2mm aluminum sheet similar to aluminum can material; (6) a 3-hole paper punch; (7) resistors for LED and the supply voltage combinations; and (8) online access to http://led.linear1.org/led.wiz, for an LED array calculator to compute the resistors required.

    

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Remove the white cement on the bulb pins
Twist the tip of a small screwdriver in the white cement around the bulb pins until loosened and continue to remove enough cement to release each pin.

    

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Remove the bulb
Place the bulb face-down on a flat surface and strike the two bulb pins with a hammer until the bulb inside releases leaving the reflector empty. Insert the flat tipped screwdriver at ether of the two spots marked on the picture around the hard drive pry at them as needed to release the adhesive on the inside of the top.

    

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Fabricate the LED support
The LED support requires a template that can be made OR downloaded as an attached PDF file featuring all the layouts for this kind of bulb. Graphic software will evenly distribute the 5mm holes on the disc. The disk size is up to you. More led's will require larger disks. Print the template on paper and cut it out with paper scissors. Place it on the aluminium sheet and light glue it on its surface. This will be useful to cut the disc properly. Take the aluminium sheet and cut out the holes using a office perforator. I found out mine cuts exactly 5mm holes in paper so for 5mm LED's it's perfect. Keeping it upside down, place the template along with the aluminium disc glued on it inside it. Cut out the holes after aligning the circles in the cutting hole. For this tutorial, I'll use 22 LEDs and a disk diameter of 4 cm. In this picture you can see another disk I made for 15 LEDs. This is neither a heatsink nor will this kind of LED bulb will not heat at all because the dissipated power is small.

    

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Fabricate the LED support
The aluminum sheet will serve as a light reflector and a holder for LEDs in the same time so take care not to bend it. After cutting out the holes its time to see how the led's should be connected. Calculate at http://led.linear1.org/led.wiz and fill in the fields with your parameters. Review the screenshot of the wizard's recommendations for an array of 22- 12V LEDs.

    

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Assembling the LED plate
Place the aluminum disc in some holding device. Hold the disc by its outer rims. For example, a pipe section with proper diameter will do. Insert the LED's into the holes with the legs up and arranged in such a manner that one cathode is next to another anode. This will make soldering easy. Don't forget this or you will have great difficulties soldering them according to the scheme. Place one drop of Super Glue on each led margin and continue arranging the other ones without accidentally applying super glue on the LED legs. When you'll have to solder the legs, these will be heated and the glue will give off a little colourless smoke with major effects on your eyes!

    

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Completing connections
After all LED's are placed and glued, put compound glue around each LED for a solid result. It is necessary to glue them firmly since the legs will have to be bended and you'll risk some leds to come off otherwise. The glue should harden for 24 hours before proceeding. Cut out the LED legs, keeping in mind that one anode will have to be bent over to the next cathode and so on. Also take care not to confuse the two of them. You can check that with one multimeter set to diodes. As the scheme advises, making 5 strings of 4 LEDs each and one string of two. Since I arranged the leads in such a fashion that one cathode is next to another anode, this operation is much easier. After soldering one string, keep the end legs at different lengths to easily identify the positive (+) and negative (-) ends. Cut the LED legs and bend each leg to the next leg. The positive (+) connects to a negative (-) and so on until each string is complete.

    

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Solder the resistors
Solder the resistors vertically to the negative (-) ends after all the strings are made according to the scheme of six positive (+) ends longer than the six negative (-) ends. Bend the longer legs toward each other and solder all the positive (+) ends together keeping some space to prevent short-circuits. Solder these joints quickly to minimize heat transfers through the LED ends that could cause damage when so close to the base. While soldering the resistors legs to each other in order to get a single negative (-) end that goes to all the strings, maintain a low profile so that the LED bulbs fit. Solder the final legs. Use copper wire (thicker) and keep in mind that one negative (-) end should be shorter. These solder joints increase rigidity that can be further stabilized by optionally filling the gaps with a hot glue gun to so that no wire accidentally touches another.

    

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Replace the LED disc
Put the LED disc inside the empty bulb, which is an exact fit if a low profile was maintained when soldered. When the disc touches the inner reflector, fill the space around the legs coming out of the bulb with as much compound glue it will hold. Any glue that increases consistency will suffice regardless of whether it is a bi-component adhesive. Allow the glue to thoroughly harden because the strength of this bond will be the only thing that holds the bulb in one piece. After hardening, use a permanent marker to write on the base the positive (+) and negative (-) legs as well as the intended voltage consumption.

    

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Notes
Cut the legs to equal the original bulbís leg-length. Connect the bulb to a twelve volt (12V) DC source such as a battery or transformer of that voltage. The image displays less light than actually generated. Any type of 5mm LED can be used to make LED bulbs if know the forward voltage and current from which to calculate resistors. These LED bulbs can also be made in blue, red, yellow and white. Six volt (6V) LED bulbs can be used in flashlights, replacing the entire flashlight mirror with one of these bulbs. In this case, the current consumption should be 220 mA however; only 200 mA was measured by multimeter. Each led BULB generates virtually no heat and the most powerful light output takes 12V@200mA and has 6 pieces of 0.5W LED's. The type of LED's used is important since a more dispersed light will be better than a concentrated one. You could also file the LEDs prior to making the bulb so as to have a more uniform light. These LED bulbs can also be driven by 12V AC with a 50Hz flicker, whereas the best results come from 12V DC.